1. Field
Embodiments of the present disclosure relate to an interior permanent magnet (IPM) motor having a permanent magnet provided in the rotor.
2. Description of the Related Art
Motors are widely used in home appliances including a laundry machine, a refrigerator, an air conditioner, and a cleaner. They are used even in electric vehicles and hybrid vehicles, which have recently attracted attention.
Among the motors, a permanent magnet motor employing a permanent magnet rotates a rotor using magnetic interaction between a magnetic field produced by a coil through which electrical current flows and a magnetic field produced by the permanent magnet.
The permanent magnet may be demagnetized by the magnetic field produced by the coil. In other words, the magnetic field produced by the coil may magnetize the permanent magnet in the opposite direction, or may weaken the magnetic field strength of the permanent magnet.
Such demagnetization effect is permanent and is not eliminated unless the permanent magnet is magnetized in the original direction.
In addition, when demagnetization of the permanent magnet occurs, the strength of the magnetic field produced by the permanent magnet is weakened. Thereby, the output torque of the motor may be reduced.